CN106971862B

CN106971862B - Polyelectrolyte in energy storage devices, products, and uses thereof

Info

Publication number: CN106971862B
Application number: CN201610995529.0A
Authority: CN
Inventors: 支春义; 黄燕
Original assignee: City University of Hong Kong CityU
Current assignee: City University of Hong Kong CityU
Priority date: 2015-11-30
Filing date: 2016-11-11
Publication date: 2020-06-16
Anticipated expiration: 2036-11-11
Also published as: CN106971862A; US20170154737A1; US9972451B2

Abstract

A novel multifunctional polyelectrolyte, particularly suitable for solid-state supercapacitors, is obtainable or obtained by reacting effective amounts of vinyl mixed silica nanoparticles (VSNPs) with a compound having acrylic-based structural units or structural units derived therefrom in the presence of a polymerization initiator. The polyelectrolytes allow for advantageously tunable ionic conductivity, superior self-healing and super-ductility. An energy storage device, particularly a solid state supercapacitor, includes a polyelectrolyte. Also disclosed is a method for producing a solid-state supercapacitor and for repairing a solid-state supercapacitor having a crack. Benefit from the superior performance of the polyelectrolyte. The above-based energy storage device can exhibit highly advantageous ductility and self-healing and superior performance compared to generally known devices.

Description

Polyelectrolyte in energy storage devices, products, and uses thereof

Technical Field

The present invention provides a novel multifunctional polyelectrolyte, particularly a polyelectrolyte suitable for solid-state supercapacitors, and a method for preparing the same. The invention further relates to a polymerizable composition for forming the polyelectrolyte. Further described is an energy storage device, in particular a solid-state supercapacitor, comprising said polyelectrolyte and a method for producing a solid-state supercapacitor and repairing it.

Background

Super-ductility and self-healing are generally desirable characteristics of materials, particularly in energy storage devices. However, only a few materials generally provide high ductility and high self-healing capacity, if any. The materials described hitherto as being more useful as malleable or self-healing materials include, for example, the malleable polymers based on ionically and covalently cross-linked alginates and polyacrylamides described by Sun et al, and the aminoethylimidazolines, di (aminoethyl) ureas and diaminotetraethyltriureas mentioned by Cordier et al (Sun et al, Nature,2012,489:133-136and Cordier et al, Nature,2008,451, doi:10.1038/Nature 06669). Nevertheless, a different challenge is to provide a material that is also suitable to act as an indispensable electrolyte in energy storage devices such as solid-state supercapacitors, i.e. it is suitable to act as a material that allows self-healing and ductility of the device, as well as at the same time as an electrolyte.

The repair properties and ductility of solid-state supercapacitors provided to date are fundamentally limited, although it is a challenge to find a capacitor with both self-repair and ductility as already explained. In addition, the self-healing or ductility typically obtained is not sufficient for many purposes. However, the design of devices with self-healing and super-ductility is a critical feature that allows new and unprecedented applications, and in particular portable and wearable supercapacitors accompanied by self-healing or ductility, on the one hand, and in particular the need for personalized electronic devices, on the other hand, because of their high power density, fast charge-discharge times, and long cycle life, as well as the above-mentioned functions.

Heretofore, self-repairing polymeric materials or external stimuli such as heating and light irradiation have been used for mechanical and electrical restoration of the device. In the reported devices, an indispensable electrolyte layer between two electrodes has been applied to the electrodes or used as a matrix for self-healing supercapacitors, usually in addition to an additional self-healing polymer layer. However, a key disadvantage of one of these self-healing supercapacitors is the low healing efficiency and cycling capability. The performance of these capacitors is typically reduced by 10% after only a few disruptions and repairs. Another highly desirable feature that disappears in these devices is the appropriate and convenient volume/mass organization due to the use of an additional component and a more complex and productive process.

To introduce ductility into generally rigid supercapacitors, further approaches to finding ductility have involved modifying the structure (e.g., non-coplanar buckled serpentine and corrugated structures, infiltrated nanostructured films) and inert electron-/ion-ductile matrices (such as elastomers and ductile textiles). Such as in CN103400702 or KR 101476989. However, the ductility of the respective devices that can be achieved is typically much less than 100%.

All of the above limitations are due fundamentally to the fact that the wide range of polyvinyl alcohol (PVA) -based acidic electrolytes for solid-state supercapacitors are neither repairable nor sufficiently malleable with unsatisfactory performance consequences, thus requiring the construction of suitable devices, additional components and high complex multi-step preparation.

Therefore, there is a strong need for multifunctional electrolytes, for example for energy storage devices, which electrolytes are self-healing and highly ductile in all electrolytes. In particular, there is a need for supercapacitors suitable for solids having suitable ionic conductivity, which simultaneously ensure sufficient self-healing and ductility of those devices to allow highly demanding further applications.

Disclosure of Invention

The present invention provides a method for preparing a polyelectrolyte by reacting an effective amount of each of the following compounds to link the compounds:

compound a) is a vinyl mixed silica nanoparticle (VSNP); especially VSNPs having an average diameter of less than 10 nm;

compound b) comprises structural units based on or derived from acrylic acid, i.e. structural units of formula (I) or derived therefrom:

in particular a compound b) of an acrylic monomer of formula (II)

The reaction is carried out in the presence of a polymerization initiator. The method of the present invention comprises the steps of:

a) providing an aqueous dispersion of said compound a);

b) adding a compound b) and said polymerization initiator, in particular ammonium persulfate, to the dispersion obtained in step a) and stirring at a temperature of less than 10 ℃;

c) the polymerization is carried out at a temperature of greater than 20 ℃.

d) Optionally having a concentration of at most 70 wt.% of phosphoric acid, to soak the polymer obtained from step c).

The invention further provides a polyelectrolyte obtainable and a polyelectrolyte obtained by said process, in particular a polyelectrolyte suitable for supercapacitors, in particular solid-state supercapacitors, respectively.

In addition, the present invention provides a polyelectrolyte comprising and specifically consisting of:

structural unit of formula (III)

Wherein n is an integer of at least 2;

vinyl mixed silica nanoparticles (VSNPs);

optionally phosphoric acid and an ortho proton derived from phosphoric acid, respectively; and

optionally water, typically non-ionic water, especially deionized water.

In another aspect, the present invention relates to a polymerizable composition for forming a polyelectrolyte comprising compound a), compound b) and ammonium persulfate and to a method for producing a polyelectrolyte from a polymerizable composition. The method comprises the following steps:

a) stirring the polymerizable composition at a temperature of less than 10 ℃;

b) carrying out the polymerization at a temperature greater than 20 ℃;

c) and optionally soaking the polymer obtained in step b) in phosphoric acid having a concentration of at most 70 wt%.

The prepared polyelectrolytes allow for advantageously tunable ionic conductivity, excellent self-repair triggered by the formation of a large number of hydrogen bonds at the carboxyl-mediated interface, and superior ductility. The polyelectrolyte can extend more than 36-fold without visible cracks, which is more ductile than common highly ductile polymers, indicating an effective strengthening mechanism by reversible crosslinking interactions of pressure transfer and energy dispersion.

Once cut, the polyelectrolytes of the invention can be repaired simply by self-repairing by pulling the fracture interfaces together at room temperature, i.e. at room temperature and under mild pressure, and after several fractures and repairs the repaired sample still shows excellent ionic properties similar to the original sample, meaning a complete self-repair.

The advantageous properties of the polyelectrolytes according to the invention result in particular from the special polymer network, in particular from VSNPs-assisted toughening and additional hydrogen bonding crosslinking. I.e. the polymeric compound b) chains are double cross-linked by hydrogen bonding as well as by VSNPs, which leads to highly advantageous properties of the resulting polyelectrolytes.

Accordingly, the present invention provides a superior polyelectrolyte that can be highly advantageous and promising in many fields such as energy storage and bio-mimicking sensing when producing multifunctional devices such as super-malleable energy storage devices and/or self-healing energy storage devices, especially portable and wearable multifunctional devices with extreme self-healing and ductility.

In another aspect of the invention, the invention provides an energy storage device comprising a polyelectrolyte of the invention, particularly a solid state supercapacitor further comprising two polypyrrole-deposited carbon nanotube paper electrodes.

Still further, the present invention relates to a method for producing a solid-state supercapacitor. The method comprises the step of placing two polypyrrole-deposited carbon nanotube paper electrodes on each side of a film of the polyelectrolyte of the invention.

The present invention further provides a method for repairing a solid-state supercapacitor having two polypyrrole-deposited carbon nanotube paper electrodes and a polyelectrolyte of the invention, wherein the solid-state supercapacitor further has at least one crack on the outer supercapacitor surface ("outer crack region") that penetrates at least through the polypyrrole-deposited carbon nanotube paper electrodes into the polyelectrolyte. The method comprises laying at least one carbon nanotube paper in the outer crack region such that the outer crack region is at least partially and in particular completely covered by the carbon nanotube paper.

The energy storage devices, especially solid state supercapacitors, based on the polyelectrolytes of the invention exhibit superior performance. They can self-heal without the aid of any additional self-healing material and maintain healing efficiency at about 100% even after several cycles of fracture and healing.

The solid-state supercapacitor of the present invention is efficiently and easily assembled by using the new polyelectrolyte and polypyrrole-deposited carbon nanotube paper electrode without damaging the capacitance. I.e., the manufacture of the self-healing supercapacitors typically takes only a few minutes and does not require additional components such as binders or release agents. These supercapacitors provide superior tunable performance in versatility, super ductility and excellent self-healing by combining with a simple pre-extended corrugated structure that has reinforcement and can provide small carbon nanotube patches for external cracks that may occur.

In the present invention, the application of the special pre-stretched structure and the highly flexible polypyrrole-deposited carbon nanotube paper electrode results in a particularly excellent capacitance even at low strain forces, very suitable for use in high performance super-ductile devices. Unlike the rigid supercapacitors commonly used, the design of the highly elastic system of the present invention has multiple functions in a single device and can be easily produced in a few steps.

Drawings

FIGS. 1(a) and (b) are schematic views showing the preparation of a polyelectrolyte according to the present invention. FIG. 1(a) shows exemplary preparation of VSNPs from vinyl-triethoxysilane. FIG. 1(b) illustrates exemplarily VSNPs-PAA polyelectrolytes from VSNPs as cross-linking agent, acrylic monomer as compound b), ammonium persulfate as polymerization initiator and phosphoric acid as pH and water content regulator. The large circles represent VSNPs, the chains between the smaller circles represent PAAs, showing that the hydrogen bonds between PAA chains connect the PAA chains as lines and that the positive protons are circles within the VSNP-PAA network, the black circles along the PAA chains being illustrated as anions.

Figures 2(a) to 2(h) relate to the physicochemical properties of certain VSNPs-PAA polyelectrolytes. FIG. 2(a) is a graph showing the ionic conductivity of VSNPs-PAA polyelectrolytes in relation to the water content wt%, i.e., the weight of water in the polyelectrolytes relative to the weight of PAA. Figure 2(b) shows the stress-strain curve of VSNPs-PAA with a moisture content range of 150 wt% in the polyelectrolyte, i.e. the weight of water in the polyelectrolyte relative to the weight of PAA in the polyelectrolyte. Figure 2(c) shows VSNPs-PAA in both relaxed (upper) and extended (lower) states. FIG. 2(d) is a schematic view to further explain the super-ductility of the polyelectrolyte of the present invention. Fig. 2(e) is a diagram showing the self-healing process of VSNPs-PAA of the present invention. FIG. 2(f) is a graph showing the self-repair of the polyelectrolyte VSNPs-PAA of the present invention (3.4mm thick and 1.8cm wide) to fully support the ca.500g mass, which is equivalent to a stress of 80kPa before repair (left) and at the third fracture/repair cycle (right). The red rectangle indicates the wound/repair site. Fig. 2(g) is a graph showing the ionic conductivity of the VSNPs-PAA polyelectrolyte of the present invention after multiple fracture/repair cycles. FIG. 2h is a schematic representation of the self-repair of the polyelectrolyte of the present invention due to hydrogen bonding at the interface.

Fig. 3(a) to 3(h) relate to the electrochemical behavior of VSNPs-PAA polyelectrolytes of the present invention. FIG. 3(a) is a schematic of a solid-state supercapacitor of the invention comprising a VSNPs-PAA polyelectrolyte between two PPy-CNT paper electrodes. Fig. 3(b) is an SEM image of the CNT paper. FIG. 3(c) is an SEM image of PPy electrodeposited on CNT paper (inset is an SEM image of a cross-section of PPy electrodeposited on CNT paper. scale: 50 um). FIG. 3(d) shows CV curves from 10mV/s to 1000mV/s at various scan frequencies. FIG. 3(e) shows the GCD curve at various charge/discharge currents, (from 0.1mA to 5 mA). Fig. 3(f) shows a graph of specific capacitance at various scan speeds depending on the water content and the presence of phosphoric acid. Fig. 3(g) shows a graph of specific capacitance at various charge/discharge currents, depending on the water content and the presence of phosphoric acid. FIG. 3(h) shows Nyquist plots for assembled ultracapacitors with various water contents.

Fig. 4(a) to 4(e) illustrate the self-healing behavior of solid-state supercapacitors, which include VSNPs-PAA polyelectrolytes. Fig. 4(a) shows an improvement of the outer surface of the supercapacitor and a method for repairing the supercapacitor by attaching a CNT paper to the outer crack region, respectively, i.e., self-repairing of the supercapacitor by attachment assistance. FIG. 4(b) shows the CV curve at a scan rate of 5mV/s after multiple fracture/repair cycles. Figure 4(c) shows the repair efficiency calculated from CV (circle) and GCD (pentagon/star) curves after multiple fracture/repair cycles. Figure 4(d) shows a GCD curve of charge/discharge current at 1mA after multiple fracture/repair cycles. Fig. 4(e) is a photograph of three series connected supercapacitors driving an LED glass bulb after self-healing. Fig. 5(a) to 5(h) relate to the electrochemical performance of supercapacitors comprising VSNPs-PAA polyelectrolyte solid state under super extension and extrusion. FIG. 5(a) is a schematic illustration of the fabrication of the super-malleable solid state supercapacitor of the present invention. Fig. 5(b) shows SEM images of relaxed PPy-CNT paper electrodes after pre-extension. FIG. 5(c) shows the CV curve under various scanning speeds of 0.1V/s for tensile strain from 0% to 600%. Figure 5(d) shows the GCD curves under various charge/discharge currents at tensile strains from 0% to 600% at 2.5 mA. Fig. 5(e) is a graph relating to the capacitance enhancement ratio obtained from the CV curve relating to tensile strain. Fig. 5(f) is a graph showing the enhancement ratio with respect to capacitance obtained from the GCD curve relating to tensile strain. Fig. 5(g) shows a graph of specific capacitance versus charge/discharge current under various compressive strains (inset illustrates the guidance of applied pressure). FIG. 5(h) shows Nyquist plots of the supercapacitors at various compressive strains.

FIG. 6 shows a Transmission Electron Microscopy (TEM) image of a highly monodisperse vinyl mixed silica nanoparticle (VSNPs) with an average diameter of 3 nm.

FIG. 7 shows Raman spectra of CNT and PPy-CNT.

Fig. 8 shows a graph of specific capacitance calculated from CV and GCD curves of a PPy-CNT paper electrode using a VSNPs-PAA polyelectrolyte film of the present invention having a water content of 507 wt%.

Fig. 9(a) and 9(b) show CV and GCD curves, respectively, using VSNPs-PAA (dots) and PVA (dashes) as electrolytes (polymer: phosphoric acid: water) with the same mass ratio. Fig. 9(a) shows CV curves with the same mass ratio (polymer: phosphoric acid: water) using VSNPs-PAA (dots) and PVA (dash) as solid electrolytes. Fig. 9(b) shows a GCD curve using VSNPs-PAA (dots) and PVA (dash) as solid-state electrolytes with the same mass ratio (polymer: phosphoric acid: water).

Figure 10 shows CV curves with various water contents from 1.75 to 507 wt%, i.e. the weight of water in the polyelectrolyte relative to the weight of PAA, at a scan rate of 25 mV/s.

FIGS. 11(a) and 11(b) show CV and GCD curves for an unlanded supercapacitor before (solid line) and after (dashed line) a 1st break/repair cycle, respectively. FIG. 11(a) shows CV curves for an unattached supercapacitor before (solid line) and after (dashed line) a 1st rupture/repair cycle, at scan frequencies of 10 and 5mV/s, respectively. Figure 11(b) shows GCD curves for an unattached supercapacitor before (solid line) and after (dashed line) one rupture/repair cycle, with charge/discharge currents of 1 and 0.5mA, respectively.

Fig. 12 shows a graph of the repair efficiency for a self-repairing supercapacitor involving the present invention with (solid line) and without (dotted line) patches, calculated from CV (rectangle) and GCD (circle) curves.

FIG. 13 shows CV curves for comparative supercapacitors using VSNPs-PAA electrolyte (dash) at a scan rate of 5mV/s, and PDMS (dot) at a scan rate of 100 mV/s.

Fig. 14(a) and 14(b) show a comparison of CV and GCD curves, respectively, for supercapacitors having VSNPs-PAA polyelectrolytes of various thicknesses. Figure 14(a) shows CV curves for supercapacitors with VSNPs-PAA polyelectrolytes of various thicknesses. Figure 14(b) shows GCD curves for supercapacitors of VSNPs-PAA polyelectrolytes of various thicknesses.

Figure 15 shows the GCD curve of a supercapacitor under various compressive strains at a charge/discharge current of 0.5 mA.

Detailed Description

In a first aspect the present invention provides a process for preparing a polyelectrolyte by reacting an effective amount of each of the following compounds to link the compounds:

compound a) is a vinyl mixed silica nanoparticle (VSNP); and

wherein

Respectively, refer to optional bonds and groups.

The reaction is carried out in the presence of a polymerization initiator, i.e. the compounds a) and b) are polymerized and linked together, respectively, in the presence of an initiator, forming a polymeric network of VSNPs from polymeric chains, preferably polyacrylic acid (PAA) chains, i.e. chains consisting of structural units of formula (III), as cross-linking points and compounds b.

Wherein n is an integer of at least 2.

The process of the invention achieves the advantageous synergistic effect that VSNPs act as covalent cross-linking points and stress transfer centers, i.e. strengthen the resulting polymeric network under great tension, wherein the compound b) polymeric chains, preferably polyacrylic acid (PAA) chains, are formed simultaneously providing excellent intra-as well as inter-molecular hydrogen bonds, also referred to as "hydrogen-bonding cross-linking". I.e. the polymeric chains of compound b), preferably PAA chains, are connected by hydrogen bonding and VSNPs double cross-linking.

The hydrogen bonding cross-linking has proven to be very advantageous for the resulting self-healing properties of the polyelectrolyte. In addition, the broken intermolecular hydrogen bonds can dynamically recombine under extension to disperse energy and homogenize the network. Phosphoric acid acts as a regulator of the water and proton ion content, which water and proton content allows a favorable adaptation of the ionic conductivity. The synergistic effect results in the observed multiple functions of super-ductility and self-healing from the polyelectrolyte.

Known and commercially used electrolytes typically have a random coil configuration below the relaxed state. Once the applied extension reaches a certain degree, the polymer chains become difficult to unravel. The energy is then at best dissipated by the rupture of the entangled polymer chains. In the polyelectrolytes described in the present invention, the stress exerted by the fixed VSNPs dispersion retards the propagation of cracks, resulting in a high degree of ductility. The polyelectrolytes can dynamically break and recombine to disperse energy, especially due to intermolecular hydrogen bonds as reversible physical cross-linking points. This dynamic process reorganizes the polymer chains and from there distributes the applied stress rapidly and uniformly throughout the network through the VSNPs acting as stress transmission centers. Said intermolecular hydrogen bonds in the cross-linked polymer chains of compound b) on VSNPs are also responsible for the superior self-healing properties obtained.

The term VSNPs, i.e. vinyl mixed silica nanoparticles, is known to the skilled person and methods for preparing the same are known, for example the methods described by Shi et al (Shi et al, J Mater Chem B,2015,3: 1187-. Generally, the term "nanoparticle" is used to refer to a particle having a diameter of less than 1000 nm. The VSNPs, i.e. compound a), preferably have an average particle size of less than 500nm, further preferably at most 100nm, even further preferably at most 50nm, and most preferably less than 10 nm. In a specific embodiment, the average diameter of the VSNPs is about 3 nm. The skilled person is familiar with the methods for determining the mean diameter and can select a suitable method. The average diameter preferably involves measuring an average diameter of at least 20 VSNPs, especially at least 50 VSNPs. One suitable method includes transmission electron microscopy. Smaller VSNPs have been shown to support greater stress, i.e., increasing the surface area allows for increased density of crosslinking sites in the polymeric structure.

Compound b) is preferably an acrylic monomer, i.e. compound b) is preferably of formula (II):

the amount of compound a) relative to the amount of compound b), in particular acrylic monomers, is preferably between 0.1% and 5% by weight, more preferably between 0.1% and 1% by weight, even more preferably between 0.1% and 0.8% by weight, and especially between 0.1% and 0.5% by weight and in a particular preferred embodiment of the invention about 0.1% by weight relative to the weight of compound b). When the content of the compound a) becomes too high, the average polymer length of the chains of the compound b) may decrease while decreasing the flexibility of its chains, but if the amount of the compound a is too low, the number of crosslinking points is decreased and less stress is adsorbed by the polyelectrolyte.

The polymerization initiator is preferably ammonium persulfate. In general, the process of the invention does not use external crosslinking agents, in particular NO ion-adding crosslinking agents such as Fe (NO)₃)₃. I.e. compound a), i.e. VSNPs, are preferably used as the sole crosslinking agent for the process.

The method for preparing the polyelectrolyte comprises the following steps:

providing an aqueous dispersion of said compound a;

adding a compound b and a polymerization initiator to the dispersion obtained in step a, stirring at a temperature of less than 10 ℃;

carrying out the polymerization at a temperature greater than 20 ℃;

optionally soaking the polymer obtained from step c in phosphoric acid, preferably at a concentration of up to 70wt. -%.

Step a generally comprises the preparation of a compound a from vinyl-triethoxysilane (VTES) as a silica precursor, preferably by a sol-gel process, which is known to the person skilled in the art. In the process of the invention, VTES is preferably added to a solvent, preferably the solvent comprises, and more preferably consists of, water. The water is preferably deionized water. Preferably, VTES is added to the solvent with stirring. More preferably, stirring is performed until the oily-like droplets completely disappear, and a transparent dispersion is obtained. Thus, stirring is preferably carried out for at least 5h, preferably at least 10 h. In a specific example, stirring is carried out for about 12 hours. Preferably, the stirring is carried out at a temperature of from 15 ℃ to 30 ℃, more preferably at a temperature of from 18 ℃ to 28 ℃, even more preferably at a temperature of from 20 ℃ to 27 ℃, especially at 25 ℃ +/-2 ℃.

In step b), the compound b) and a polymerization initiator are added to the dispersion obtained in step a). This preferably means that the compound b) and the polymerization initiator are added simultaneously or that one of them is added immediately after the addition of the other. The temperature in step b) is preferably less than 8 deg.C, more preferably less than 5 deg.C. In a specific embodiment, the temperature is about 0 ℃ to 4 ℃. Preferably, during stirring of the reaction mixture in step b) after addition of compound b), and the polymerization initiator is degassed and sealed under an inert gas, preferably under nitrogen, which allows further removal of dissolved oxygen. In a preferred embodiment of the invention, compound b) is purified, in particular by distillation under reduced pressure, before addition to the dispersion obtained in step a). Further preferably, compound b) is kept in a refrigerator before addition to the dispersion obtained in step a).

Step c) is generally referred to as the extension step. The temperature in step c), i.e. during the polymerization, is preferably at least 30 ℃, more preferably at least 30 ℃ and at most 45 ℃. In a specific embodiment, the temperature is 36 ℃ to 40 ℃. Step c) is preferably carried out for at least 12h, more preferably at least 24h, further preferably at least 28 h. In a particularly preferred embodiment, step c) is carried out for about 30 h.

Preferably, the process further comprises the addition of water, typically deionized water, which is effected in step d), either immediately after step c) or immediately after step d) as the polymer from step c) is soaked in phosphoric acid, or as a separate step. Preferably, water is added so that the water content of the polyelectrolyte reaches at least 20 wt.%, further preferably at least 50 wt.%, preferably at least 100 wt.%, more preferably more than 100 wt.% and even more preferably more than 300 wt.%, relative to the weight of compound b). In particular, the water content is 450 to 550 wt%, such as about 507 wt%. As the water content increases, the movement of ions in the polymeric network, preferably the VSNPs-PAA network, becomes easier and its chains are more sufficiently extended. Therefore, the ion conductivity is significantly increased with the water content, and it is sufficiently shown that the polyelectrolyte of the present invention can be used as an electrolyte for a supercapacitor as compared to commonly used electrolytes such as polyvinyl alcohol-based electrolytes. The term "water content" refers to the polyelectrolyte as used herein, referring to the amount of water relative to the weight of compound b) as used for preparing the polyelectrolyte, unless otherwise defined. In a preferred embodiment, the compound b) is an acrylic monomer, and therefore, in said embodiment, said water content relates to the weight of water relative to the weight of acrylic monomer used for preparing the polyelectrolyte and to PAA in the polyelectrolyte, respectively.

In a further aspect, the present invention provides a polyelectrolyte obtainable and obtained by the process of the invention described above, respectively, wherein compound b) is preferably an acrylic monomer and compound a) preferably means VSNPs having an average diameter of less than 500nm, further preferably at most 100nm and especially preferably less than 10nm, especially about 3 nm. The polyelectrolyte preferably further comprises water, especially deionized water, and phosphoric acid.

The polyelectrolytes are preferably suitable for energy storage devices, in particular for supercapacitors, in particular solid-state supercapacitors. Ionic conductivity of polyelectrolyteIs preferably at least 10^-4S/cm, especially at least 10^-3S/cm, and preferably about 0.0075S/cm, at room temperature, i.e. between 20 ℃ and 25 ℃, preferably at 25 ℃ +/-2 ℃. The polyelectrolyte may preferably be extended at least 30 times, more preferably at least 36 times without any visible cracks, i.e. without any crack formation visible by normal eye force during extension as determined by inspection.

The skilled person is aware of the term polyelectrolyte, usually understood as a polymer, whose repeating units have electrolyte groups. The skilled person is also aware of the terms supercapacitor and solid-state supercapacitor, respectively.

The invention further relates to a polyelectrolyte comprising and particularly preferably consisting of:

a structural unit of formula (III):

wherein n is an integer of at least 2;

vinyl mixed silica nanoparticles (VSNPs); and

alternatively, phosphoric acid and protons derived from phosphoric acid, respectively; and

alternatively, water, typically deionized water;

wherein the structural units of the formula (III) are preferably crosslinked by VSNPs and by intermolecular and intramolecular hydrogen bonds of the structural units of the formula (III). Thus, the polyelectrolyte preferably comprises a double cross-linked polymeric network, also known as a "VSNPs-PAA network". Generally, no ionic bonds are formed in the VSNPs-PAA network and, therefore, preferably no ionic bonds are present in the polyelectrolyte.

Preferably, the polyelectrolyte further comprises phosphoric acid or water, typically deionized water, particularly preferably phosphoric acid and water. The water content of the polyelectrolyte is preferably at least 20 wt%, further preferably at least 50 wt%, preferably at least 100 wt%, further preferably more than 100 wt%, more preferably more than 300 wt% and especially 450 to 550 wt%, such as about 507 wt%, i.e. the weight of water in the polyelectrolyte relative to the weight of PAA.

The polyelectrolyte may preferably be extended more than 30 times, more preferably more than 36 times without any cracks, i.e. without any crack formation visible by normal eye force during extension as determined by inspection. The polyelectrolyte is self-healing, preferably self-healing under mild pressure, such as by simply contacting the wound network without the application of pressure, and at a temperature between 20 ℃ and 30 ℃, more preferably between 23 ℃ and 27 ℃, and especially at about 25 ℃, when cut under ambient conditions. The term "self-healing" according to the invention refers to the properties of the material, i.e. once the network is created, it breaks to form at least two interfaces (also called "wounds"), reestablishing the properties of the polymeric network, in particular connecting them by hydrogen bonds at the interfaces between said interfaces. The reconstruction network is preferably capable of withstanding a pressure of, for example, 80kPa, preferably at least 80 kPa.

Preferably, the polyelectrolyte has an initial ionic conductivity of at least 80%, more preferably at least 85%, after one repair cycle, i.e. the ionic conductivity has a complete polymeric network without wounds. More preferably, the polyelectrolyte has an initial ionic conductivity of at least 75%, more preferably at least 80%, after the second repair cycle. The ionic conductivity of the polyelectrolyte after three repair cycles and more preferably at least 75%, more preferably at least 80% of the initial ionic conductivity after four repair cycles.

The polyelectrolyte is preferably suitable for energy storage devices, more preferably for supercapacitors and solid-state supercapacitors, respectively.

The invention further provides a polymeric composition for forming a polyelectrolyte comprising effective amounts of compound a), compound b) and ammonium persulfate. The polymeric composition preferably comprises a solvent, more preferably water, especially deionized water. Also according to the present invention is a method of producing a polyelectrolyte from said polymeric composition, the method comprising the steps of:

stirring the polymeric composition at a temperature of less than 10 ℃, preferably less than 5 ℃, and more preferably from about 0 ℃ to about 4 ℃; and

said polymerization is carried out at a temperature greater than 20 ℃, more preferably greater than 30 ℃ and still more preferably at a temperature of about 36 ℃ to 40 ℃;

optionally soaking the polymer obtained in step b) in phosphoric acid having a concentration of at most 70 wt%.

Preferably, the process for producing said polyelectrolyte from a polymeric composition according to the present invention further comprises a step immediately following step b) or immediately following optional step c), wherein water, typically deionized water, is added to said polymer obtained in step c). The compounds b) are preferably acrylic monomers and the compounds a) preferably mean VSNPs having an average diameter of less than 500nm, more preferably up to 100nm and particularly preferably less than 10nm, in particular about 3 nm.

The invention also relates to an energy storage device comprising respectively an obtainable polyelectrolyte and a polyelectrolyte obtained by reacting an effective amount of each of the following compounds, linking said compounds in the presence of a polymerization initiator.

Compound a) is a vinyl mixed silica nanoparticle (VSNP); and

wherein

Respectively, means an optional bond and a group, and wherein the reaction of said effective amount of compound a) and compound b) in the presence of a polymerization initiator comprises the steps of:

providing an aqueous dispersion of compound a);

adding compound b) and a polymerization initiator to the dispersion obtained in step a) and stirring at a temperature of less than 10 ℃;

carrying out the polymerization at a temperature greater than 20 ℃;

optionally, the polymer obtained in step c) is soaked in phosphoric acid, preferably having a concentration of at most 70 wt%.

Preferably, the reaction further comprises, after step c or step d, the step of adding water, typically deionized water, to the polymer such that the water content of the polyelectrolyte is preferably at least 20 wt.%, further preferably at least 50 wt.%, further preferably at least 100 wt.%, further preferably more than 100 wt.%, more preferably more than 300 wt.% and especially 450 to 550 wt.%, for example about 507 wt.%, relative to the weight of compound b). The presence of water or phosphoric acid, in particular water and phosphoric acid, allows a further enhancement of the specific capacitance in the electrolyte due to the increased ion mobility and the facilitated ion migration. Alternatively water may be added by soaking the polymer from step c) in phosphoric acid, i.e. in step d).

Preferably, the energy storage device is a supercapacitor, in particular a solid-state supercapacitor. The energy storage device, especially a solid-state supercapacitor, preferably further comprises at least one polypyrrole (PPy) -deposited Carbon Nanotube (CNT) paper electrode (also referred to as "PPy-CNT paper electrode" or "PPy @ — CNT paper electrode"). More preferably, the energy storage device, preferably a solid state supercapacitor, comprises two PPy-CNT paper electrodes, wherein these electrodes preferably act as both active material and as current collector. In a preferred embodiment, the energy storage device, in particular the solid-state supercapacitor, does not comprise any binder or release agent. In an embodiment of the invention, the energy storage device is a solid state supercapacitor comprising and especially consisting of a polyelectrolyte and two PPy-CNT paper electrodes.

In a preferred embodiment of the invention, the solid-state supercapacitor further comprises several patches of Carbon Nanotube (CNT) paper (further referred to as "CNT paper patches") to further support the excellent self-repair of the solid-state supercapacitor, preferably at least two CNT paper patches, typically applied on the wound, i.e. a crack existing on the outer surface of the solid-state supercapacitor, also referred to as "external crack area", which further penetrates at least one PPy-CNT paper electrode into the polyelectrolyte. The CNT paper paste has a smaller size and smaller volume, and the corresponding size depends on the size of the external crack region compared to the PPy-CNT paper electrode. The CNT paper paste comprises Carbon Nanotubes (CNTs). Preferably, the CNT paper paste comprises 98 wt% carbon nanotubes. The size of the CNT paper paste is preferably less than 1cm by 2cm, especially about 0.5cm by 1.5 cm.

The solid state supercapacitors of the invention preferably allow a repair efficiency of more than 80%, in particular more than 90%, more preferably at least 95% and especially about 100%, calculated from CV or calculated from GCD even after 20 fracture/repair cycles. As shown in fig. 4(a), one break/repair cycle includes the steps of cutting a solid-state supercapacitor into two sections such that both sections have two PPy-CNT paper electrodes and a polyelectrolyte in between, contacting, i.e. forming, the two sections at the cut boundary, and attaching the CNT paper to the outer surface of the supercapacitor in the region of the cut boundary, i.e. in the contact region of the two sections (the outer crack region), such that said region is partially or preferably completely covered by the CNT paper attachment.

The solid state supercapacitor of the invention preferably has a ductility of at least 300%, more preferably at least 400% and especially at least 600%, i.e. the solid state supercapacitor can be extended at least up to 3 times, preferably at least up to 4 times and especially at least up to 6 times compared to the initial length without finding cracks during extension and detectable by normal eye force after inspection.

The solid-state super capacitor preferably has a scan rate of 150Fg at least 5mV/s specific capacitance^-1At a scan rate of at least 130Fg at 10mV/s^-1At a scan rate of 100mV/s of at least 100Fg^-1And a scan rate of at least 25Fg at 500mV/s^-1. The solid-state supercapacitor preferably has a charge/discharge current of at least 150Fg at between 0.1mA and 2.5mA^-1And further preferably of 5mA, andat least 100Fg of charging/discharging current^-1The specific capacitance of (c).

The present invention still further provides a process for producing a solid-state supercapacitor comprising a polyelectrolyte and two PPy-CNT paper electrodes, said process comprising the step of placing the two PPy-CNT paper electrodes on opposite sides of a film of the polyelectrolyte. I.e. the PPy-CNT paper electrodes are spaced apart by the thin film, wherein the thickness of the thin film is preferably defined as the distance between two PPy-CNT paper electrodes. The skilled person is aware of the term "thin film" in the field of energy storage devices. It broadly refers to a material having a planar surface with a length and width greater than its thickness.

The polyelectrolyte is obtainable or obtained by reacting an effective amount of each of the following compounds in the presence of a polymerization initiator to link the compounds:

compound a) is a vinyl mixed silica nanoparticle (VSNP); and

wherein

providing an aqueous dispersion of compound a);

carrying out the polymerization at a temperature greater than 20 ℃;

the polymer obtained in step c) is preferably soaked in phosphoric acid, preferably having a concentration of at most 70 wt%.

The preparation of the solid-state supercapacitor is preferably less than 10 minutes, usually only a few seconds.

Preferably, the PPy-CNT paper electrode is directly connected to the film of the polyelectrolyte, i.e. the step of placing two PPy-CNT paper electrodes on opposite sides of the film of the polyelectrolyte is performed by directly connecting the PPy-CNT paper electrodes to opposite sides of the film of the polyelectrolyte. By "directly connected" is meant that no additional material is between the PPy-CNT paper electrode and the polyelectrolyte. Thus, in a preferred embodiment, no binder is used when preparing a solid-state supercapacitor. Preferably, the supercapacitor does not contain a release agent. The latter allows to further simplify the manufacture of the supercapacitor and to reduce the cost of manufacturing the same product. Preferably, the PPy-CNT paper electrode has a corrugated structure such as illustrated in fig. 5 (b).

The thickness of the thin film of polyelectrolyte is preferably less than 10mm, more preferably less than 8mm and especially from 2mm to 6 mm. The thickness of the PPy-CNT paper electrode is preferably less than 100nm, further preferably less than 90 nm. Such a size of the PPy-CNT paper electrode allows further increased ion transport during charging and discharging.

Preferably, the method for producing a solid state supercapacitor further comprises the step of pre-extending the film of polyelectrolyte prior to placing the PPy-CNT paper electrodes on opposite sides of the stretched-open film. The film is preferably pre-extended to at least 100%, more preferably at least 200%, more preferably at least 400% and especially at least 600% compared to the initial length. Such a pre-extension step further improves the ductility of the prepared solid-state supercapacitor. In particular, the corrugated structure of the PPy-CNT paper electrode after compression, i.e. after relaxation, avoids the drawbacks of the known devices, which strongly limit their performance due to structural rupture formed after the application of extension.

In a preferred embodiment, the process for producing a solid-state supercapacitor further comprises a step for preparing a PPy-CNT paper electrode comprising electrodepositing a CNT paper with polypyrrole, preferably from an aqueous pyrrole solution further comprising p-toluenesulfonic acid and sodium toluenesulfonate. Preferably, prior to electrodeposition, the pyrrole is distilled in order to purify the pyrrole monomer. Preferably, the electrodeposition of the CNT paper with polypyrrole is carried out at 0.8V versus Ag/AgCl, preferably for at least 5 minutes, more preferably for at least 8 minutes and especially for about 10 minutes, and preferably at a temperature of about 0 ℃. More preferably, electrodeposition is carried out in a solution with 0.1M p-toluenesulfonic acid, 0.3M sodium toluene sulfonate and 0.5% pyrrole monomer (v/v).

In a particular embodiment, the method for producing a solid-state supercapacitor consists of:

(ii) optionally electrodepositing CNT paper with polypyrrole;

selectively preparing a film of the above-described polyelectrolyte and preferably pre-extending the film;

two PPy-CNT papers were placed on opposite sides of the polyelectrolyte film, which was optionally pre-stretched.

Optionally, CNT paper patches, preferably at least two, may be laid in the crack regions possibly outside the PPy-CNT paper electrode to further support the excellent self-healing of the solid-state supercapacitors of the invention.

The invention further relates to a method for repairing a solid-state supercapacitor comprising two PPy-CNT paper electrodes and a polyelectrolyte between the two PPy-CNT paper electrodes as described above, said solid-state supercapacitor having at least one crack occurring on the outer supercapacitor surface (also referred to as "outer crack region") passing at least through the PPy-CNT paper electrodes and into the polyelectrolyte. The method for repairing a solid-state supercapacitor includes laying at least one CNT paper paste on an outer crack region such that the outer crack region is partially or preferably completely covered by the CNT paper paste. This further supports excellent self-repair of solid state supercapacitors, representing a method for self-repair supported CNT paper pasting of solid state supercapacitors. Preferably, a CNT paper is applied to an outer crack region.

The crack may further penetrate the opposing PPy-CNT paper electrodes, i.e. the solid-state supercapacitor is divided into two sections, both having two PPy-CNT paper electrodes and a polyelectrolyte in between the electrodes, i.e. forming two outer crack regions. In such an embodiment, the method further comprises contacting the two segments on the interface formed by the crack, i.e. the crack boundary, prior to laying the CNT paper on the outer crack region.

The CNT paper paste is preferably applied to the crack region at a temperature between 20 ℃ and 28 ℃, preferably at about 25 ℃ +/-2 ℃.

The examples set out below further illustrate the invention. The preferred embodiments and figures described above, and the examples given below, represent preferred or exemplary embodiments, and the skilled person will understand that these embodiments or examples are not intended to limit the invention.

Examples

Example 1a

Preparation of polyelectrolyte

VSNPs were prepared using a sol-gel method (fig. 1 a). Acrylic monomers and VSNPs were polymerized in the presence of ammonium persulfate as initiator. Phosphoric acid acts as a regulator of water and of the content of cationic protons (FIG. 1 b).

Vinyl-triethoxysilane (VTES, 3.8g, Alfa asaar) was first added to deionized water (30g) at room temperature and stirred vigorously until the oily droplets completely disappeared to obtain a clear dispersion of vinyl mixed silica nanoparticles (approximately 12 h). Acrylic monomer (6g, Beijing Chemical Reagent) and ammonium persulfate (0.012g, Xilong Chemical) were then added to the aqueous dispersion of diluted vinyl mixed silica nanoparticles (24mL, 0.125 wt%) and stirred at 0-4 ℃. Before use, acrylic acid monomers were purified by distillation under reduced pressure and stored in a refrigerator. Degassing the solution and sealing in N during magnetic stirring₂In order to remove dissolved oxygen. Subsequently, the free-radical polymerization was carried out in a water bath at 38. + -. 2 ℃ for 30 h. Finally, the polymer prepared as above was soaked in phosphoric acid (500ml, 0-70 wt%).

Example 1b

Measurement of physicochemical and electrochemical Properties of the polyelectrolyte prepared in example 1a

First, the VSPNs-PAA band was divided into two using scissors. The fresh wound is then exposed to mild pressure and placed under ambient conditions. After failure, the band successfully self-heals within minutes, and the band can be extended forcefully without breaking (fig. 2(e) and 2 (f)). After 4 fracture/repair cycles, the ionic conductivity properties were well restored (fig. 2 g). Complete self-repair is expected to be due to an abundance of reversible intermolecular hydrogen bonding crosslinks. When the disruption occurs at the contact zone, the broken hydrogen bonds can recombine together by carboxyl groups at the polyacrylic acid backbone (FIG. 2 h).

The polyelectrolyte was extended and a sample of polyelectrolyte was tested having a water content of 150 wt% in the polyelectrolyte compared to the weight of PAA. It was demonstrated that the polyelectrolyte exhibited over 36-fold elongation in the super-ductility (fig. 2(b) and 2(c)), which was higher than the known highly ductile polymers. As mentioned above, such super-ductility appears to occur due to, inter alia, VSNPs-assisted toughening and hydrogen bonding cross-linking (fig. 2 (d)).

The ionic conductivity of the polyelectrolyte was determined by measuring the resistance R of the polyelectrolyte using a multi-meter and then measuring the length L and cross-sectional area A using a ruler. The ionic conductivity was obtained by L/(R × a). Determination of the ionic conductivity for different water contents, it was demonstrated that the ionic conductivity increases significantly with water content and compared to the known polyvinyl alcohol electrolyte (fig. 2 a). As the water content increases, the movement of ions in VSNPs-PAA becomes easier and the VSNPs-PAA chains are more fully extended.

Example 2a

Preparation of a solid-State supercapacitor comprising the polyelectrolyte prepared in example 1a

To produce a PPy/CNT paper electrode, the CNT paper was electrodeposited with PPy at 0.8V vs. Ag/AgCl for 10 minutes at 0 ℃ in a solution of 0.1M p-toluene sulfonic acid, 0.3M sodium toluene sulfonate and 0.5% pyrrole monomer (V: V). Prior to electrodeposition, the pyrrole is distilled to purify the pyrrole monomer.

The VSNPs-PAA polyelectrolyte prepared in example 1a, which was in the form of a thin film having 507 wt% moisture based on the weight of PAA in the polyelectrolyte, was used as an electrolyte without additional treatment. PPy electrodeposition on CNT paper is the use as an active material and current manifold to build solid-state supercapacitors. In addition to the capacitive effect, the elastic PPy acts as a pressure cushion during extension. Under ambient conditions, two PPy-CNT paper electrodes were laid directly on the VSNPs-PAA thin film electrolyte without the use of an adhesive or release agent.

Example 2b

Determination of the physicochemical and electrochemical characteristics of the solid-state supercapacitor prepared in example 2a

The performance of the assembled supercapacitor was tested by CV and GCD in a two-electrode arrangement using a potentiostat (CHI 760E). Electrochemical Impedance Spectrum (EIS) was measured in a band from 0.01Hz to 5000Hz with an amplitude of 5mV of potential. All measurements were performed at room temperature. Specific capacitance was estimated using charging in combination with GCD and CV curves from the equations separately and compared to single electrode (Cm):

where I is the discharge current during GCD, t is the discharge time during GCD, and U is the voltage range (U ═ U-₊-U_-) M is the mass of PPy at one electrode, v is the sweep frequency of the CV curve, and i (u) is the current during CV.

The tensile strength of the VSNPs-PAA polyelectrolyte was tested by a mechanical test system (Zwick Z030). The microstructure and morphology of the electrode was characterized by Scanning Electron Microscopy (SEM) (JEOL JSM-6335F) with an acceleration voltage of 5 kV. Raman spectroscopy spectra were obtained by a RENISHAW Raman microscope at 633nm excitation wavelength.

First, the morphology of the CNT paper and the PPy-CNT paper was measured. Fig. 3(b) shows a typical morphology of CNT paper with interwoven nanowires. In contrast, a thin film of PPy was electrodeposited uniformly on CNT paper (fig. 3 c).

The PPy-deposited CNT electrodes were intentionally folded before viewing the SEM. Notably, no cracks appeared on the electrodes due to the flexibility of PPy and CNT paper.

The species prepared above were confirmed by Raman spectroscopy (fig. 7). Observed at 1314cm^-1And 1580cm^-1Two typical peaks of the CNT, which correspond to the D band (vibration of carbon atoms with sp3 electron arrangement) and G band (vibration of carbon atoms with a plane of sp2 bonds), respectively. Raman spectra confirmed the identity of PPy. At 631cm^-1The band is due to the ring twisting. At 685cm^-1The area corresponds to the C-H wobble. About 935cm^-1Corresponds to ring deformation. At 987cm^-1The bands are due to the dichation-related ring deformation. At 1059cm^-1And 1092cm^-1Corresponds to symmetric C-H plane bending and N-H plane deformation. At 1249cm^-1And 1316cm^-1Are respectively due to asymmetric C-H in-plane bending and asymmetric intra-ring C-N extension. At 1382cm^-1And 1506cm^-1Both reflect C-C and C-N extensions. Alongside the G band of CNTs, at 1580cm^-1The peak of (a) is due to the extended overlap of radical cations and dichation of C-C within the ring and C-C between the rings.

The PPy has a thin thickness of less than 90nm (fig. 3c), helping fast ion transport during charge/discharge. The TEM images (fig. 6) revealed that VSNPs were highly monodisperse by sol-gel synthesis with a mean diameter of 3 nm.

Preparation of Cyclic Voltammetry (CV) curves at up to 1000mV s^-1With various currents of 0.1-5mA (fig. 3(d) and 3(e)) and constant current charge/discharge (GCD) curves. It is noted that the scan frequencies achieved herein are much higher than the highest speeds measured for PPy-based electrodes even in aqueous electrolytes, and that CVs maintain a rectangular shape at high scan frequencies of 250 mV/s. This indicates that solid-state supercapacitors can withstand very fast rates of voltage/current change, which is assumed to be due to, for example, the excellent ionic conductivity of the polyelectrolyte and the presence of electrodes in the capacitorEfficient electrochemical dynamic process.

These CV and GCD curves were used to evaluate specific capacitance (fig. 8 and 9) which was compared to or even higher than the results of mass ratio tests at the same electrolyte composition in the liquid electrolyte. VSNPs-PAA polyelectrolyte was shown to be a highly radioactive alternative PVA as electrolyte without compromising the electrode performance.

Consistent with the water content-affected ionic conductivity in VSNPs-PAA polyelectrolytes, the CV and GCD curves proved to be significantly different at various water contents (fig. 10). At all sweep frequencies and charge/discharge currents, the capacitance varies up to four orders of magnitude with increasing water content-specific capacitance in the range of 1.75 to 507 wt.% (fig. 3(f) and fig. 3 (g)). The enhanced capacitance can be attributed to, for example, high ionic mobility in large volumes of water and convenient ionic migration at the wetted electrolyte/electrode interface. The electrochemical impedance spectroscopy performed (fig. 3(h)) also indicates this. When the water content is large, the supercapacitor shows the resistance of a small system (intercept at Z-axis) and the total resistance (at the end point of Nyquist plot) (fig. 3 (h)).

The well-extended polymer chains help transport ions at the electrolyte and electrolyte/electrode interface, thus reducing resistance and increasing specific capacitance. In addition to the water content, the positive protons that permeate into the VSNPs-PAA also contribute to the enhanced capacitance. As observed in FIGS. 3(f) - (H), it was confirmed that the water content was high without H₃PO₄The performance of the infiltrated VSNPs-PAA was worse. Their difference is more pronounced at faster scan frequencies and higher charge/discharge currents, revealing the transport of available ions in rapid electrochemical dynamic processes.

Example 2c

Determination of the self-healing Properties of the solid-state supercapacitor prepared in example 2a

To determine the self-healing properties of the supercapacitor, the solid-state supercapacitor prepared in example 2a was cut into two sections such that both sections had PPy-CNT paper electrodes and a polyelectrolyte in between. Subsequently, two segments are contacted at the cut boundary, and the CNT paper paste has been attached to the outer cracked region of the supercapacitor, i.e. in the region of the cut boundary, i.e. in the contact area of the two segments, so that the outer cracked region is covered by the CNT paper paste. A schematic of one fracture/repair cycle is shown in figure 4 a. Several fracture/repair cycles have been performed subsequently.

The electrochemical performance of the patch-assisted self-healing supercapacitor was systematically investigated. The method has been described above.

Surprisingly, both CV and GCD curves exhibited almost complete coverage even after twenty fracture/repair cycles (fig. 4(b) and (d)). The repair efficiency proved to be about 100% during all the fracture/repair times (see fig. 4(c)) very superior to other known self-repair devices. The results reveal the superiority of employing the self-healing polyelectrolytes of the present invention by conventional methods, e.g., using additional components external or internal to self-healing to facilitate self-healing. This excellent self-healing performance can also be attributed to the good conductivity of the CNT paper paste, which well connects the broken parts (fig. 11 and 12). The electrochemical performance of the non-pasted supercapacitor deteriorated after one fracture/repair cycle, revealed by smaller CV bend, less discharge time, higher resistance and distorted CV and GCD curves (fig. 11(a) and 11 (b)). At all scan frequencies and charge/discharge currents, the repair efficiency with the help of the patch proved to be superior to those without the patch (fig. 12).

Interestingly, the repair efficiency varied slightly around 100% over these fracture/repair cycles. This may be due to occasional micro-adjustment between broken electrodes. That is, macroscopic manual operation will result in occasional fine-tuning of the reconnected electrodes, resulting in small variations in performance during the fracture/repair cycle. Therefore, the super capacitor of the present invention exhibits such excellent self-repairing performance due to the use of the intrinsic self-repairing polyelectrolyte and the small CNT paste, which can satisfy the high-performance self-repairing device.

The super capacitor effectively drives the LED glass bulb after self-healing (fig. 4 (e)).

Example 3a

Preparation under super extension and extrusion of a supercapacitor comprising the VSNPs-PAA electrolyte solid state prepared in example 1a

To fabricate a super-ductile supercapacitor, the film of VSNPs-PAA polyelectrolyte prepared in example 1a was first pre-extended to 600% length. The PPy-CNT paper prepared in example 2a was then laid on the opposite side of the extended electrolyte layer. After the release, an electrode structure in which the supercapacitor had ripples was formed (fig. 5 (a)). Stably connecting the electrode to the polyelectrolyte. Due to the excellent flexibility of the PPy-CNT paper, no cracks on the corrugated electrode were observed from the SEM image (fig. 5 (b)).

Example 3b

Determination of the physicochemical and electrochemical characteristics of the solid-state supercapacitor prepared in example 3a

The methods of physicochemical and electrochemical properties already described in example 2b were used.

SEM images show the moire structure of the relaxed PPy-CNT paper electrode. The corrugated structure further avoids the disadvantages of conventional malleable devices, whose performance is generally limited by structural rupture resulting from application of the extensions.

The supercapacitor prepared in example 3a exhibited enhanced electrochemical performance under extension (fig. 5(c) and (d)). Both CV and GCD curves expand with increasing extension. The capacitance calculated from the CV and GCD curves achieves growth rates of over 100% and over 250%, respectively, tensile strain increases from 0 to 600% (fig. 5(e) and (f) — assuming a larger contact area between the electrode and the polyelectrolyte due to extension guidance is due to the increased capacitance-as shown in fig. 5(a) and (b), the presence of untouched areas on the free corrugated electrode is expected.

Polydimethylsiloxane (PDMS), a common matrix material for super-malleable devices, has been tested in comparative experiments, which revealed that PDMS failed to fulfill the role of an electrolyte due to the lack of free-moving ions (fig. 13). Compared to VSNPs-PAA, there is no CV flexure when PDMS is used as the electrolyte even at high scan frequencies of 100 mV/s.

Similar to the extended case, the specific capacitance also exhibits an increase with compressive strain (fig. 5 (g)). Since the effect of electrolyte thickness on the capacitor is negligible in the test, pressure-improved interfacial contact between the electrolyte and the electrodes should be a reason for the elevated behavior under compression. The supercapacitor proved to have a smaller system resistance (intercept in Z-axis) at higher compressive strain (fig. 5 (h)). This is also confirmed by the reduced IR drop measured and shown in fig. 15. This indicates that compressive strain further improves interfacial contact and thus ion migration from the polyelectrolyte to the surface of the electrode, which further helps to provide superior capacitance.

In addition, the CV and GCD profiles of the supercapacitors prepared in example 3a were determined at different polyelectrolyte thicknesses. The test revealed that the performance of the supercapacitor was not affected by the electrolyte membrane thickness when in the comparative range between 2mm and 6mm, (fig. 14(a) and 14 (b)).

Claims

1. A method for preparing a polyelectrolyte by reacting an effective amount of each of the following compounds in the presence of a polymerization initiator to link the compounds:

compound a) is a vinyl mixed silica nanoparticle; and

compound b) comprises the following structural unit of formula (I) or a structural unit derived therefrom:

the method comprises the following steps:

a) providing an aqueous dispersion of said compound a);

b) adding compound b) and said polymerization initiator to said dispersion obtained in step a) and stirring at a temperature of less than 10 ℃;

c) the polymerization is carried out at a temperature of greater than 20 ℃.

2. The method of claim 1, wherein compound b) is an acrylic monomer having formula (II):

and wherein the average diameter of compound b) is less than 10nm and the polymerization initiator is ammonium persulfate, and wherein the content of compound a) is between 0.1 and 0.5 wt.% with respect to the content of compound b).

3. The process of claim 1 further comprising step (d) of soaking the polymer from step c) in phosphoric acid, wherein the phosphoric acid has a concentration of up to 70 wt.%.

4. The process according to claim 1, further comprising the step of adding water to the polymer obtained in step c), whereby the water content in the polyelectrolyte is at least 100 wt.% relative to the weight of compound b).

5. The process of claim 1 further comprising the step of preparing compound a) from vinyl-triethoxysilane in deionized water by stirring at a temperature between 18 ℃ and 28 ℃ for at least 10h, and wherein the temperature in step b) is about 0 ℃ to 4 ℃, and wherein the temperature in step c) is at least 30 ℃ and at most 45 ℃, and step c) is performed for at least 24 h.

6. The method of claim 1, wherein no external crosslinker is added.

7. A polyelectrolyte obtained by the process of claim 1.

8. The polyelectrolyte of claim 7 wherein the average diameter of compound a) is less than 10nm and wherein compound b) is an acrylic monomer of formula (II)

And wherein the polyelectrolyte further comprises phosphoric acid and water.

9. The polyelectrolyte of claim 7, wherein the polyelectrolyte is suitable for use in a solid-state supercapacitor.

10. An energy storage device comprising the polyelectrolyte of claim 7.

11. The energy storage device of claim 10, wherein the average diameter of compound a) is less than 10nm and wherein compound b) is an acrylic monomer of formula (II)

And wherein the polyelectrolyte further comprises phosphoric acid and water, wherein the amount of water is at least 100 wt.% relative to the weight of compound b).

12. The energy storage device of claim 10, further comprising two polypyrrole-deposited carbon nanotube paper electrodes.

13. The energy storage device of claim 12, wherein the polypyrrole-deposited carbon nanotube paper electrode acts as both an active material and a current collector.

14. The energy storage device of claim 10, which is a solid state supercapacitor and which further comprises two polypyrrole-deposited carbon nanotube paper electrodes.

15. A method for producing the energy storage device of claim 14, comprising the step of placing two polypyrrole-deposited carbon nanotube paper electrodes on opposite sides of a thin film of polyelectrolyte.

16. The method of claim 15 wherein the step of placing two polypyrrole-deposited carbon nanotube paper electrodes on opposite sides of the thin film of polyelectrolyte is performed by directly attaching the polypyrrole-deposited carbon nanotube paper electrodes to the opposite sides of the thin film of polyelectrolyte.

17. The method of claim 15, wherein the film thickness of the polyelectrolyte is less than 8mm and the thickness of the polypyrrole-deposited carbon nanotube paper electrode is less than 90 nm.

18. The method of claim 15, further comprising the step of pre-stretching the film of polyelectrolyte prior to placing the polypyrrole-deposited carbon nanotube paper electrode on the opposite side of the film of polyelectrolyte, wherein the film is pre-stretched at least 600% compared to the initial length.

19. The method of claim 15 further comprising the step of preparing a polypyrrole-deposited carbon nanotube paper electrode comprising the step of electrodepositing CNT paper with polypyrrole in an aqueous pyrrole solution further comprising p-toluenesulfonic acid and sodium toluenesulfonate.

20. A method of repairing the energy storage device of claim 14, wherein the solid-state supercapacitor further has at least one crack occurring in the outer surface of the supercapacitor, i.e. having at least one outer crack region, at least through the polypyrrole-deposited carbon nanotube paper electrode into the polyelectrolyte, said method comprising laying at least one carbon nanotube paper in the outer crack region, such that the outer crack region is at least partially covered by a carbon nanotube paper tape.